The invention relates generally to web slitter machines of the type used for cutting a continuous web of material and, more particularly, to a device for locking the blades of such machines to facilitate maintenance and blade replacement.
Web slitters are cutting machines commonly employed to cut an endless web, such as a continuous roll of paper, to reduce the initial wide web into a series of narrower webs during winding or rewinding operations. A typical prior art web slitter for use in paper manufacturing is indicated generally at 8 in FIG. 1. Such web slitters are manufactured by the Valmet Corporation of Helsinki, Finland. As is shown in FIG. 1, the web slitter 8 includes a top blade 10 in the form of a rotary cutting disk that is suspended from a slitter frame 9 which is attached to one or more transverse bars 11 by an intermediate slitter carriage 17. An operator locks slitter frame 9 in position on slitter carriage 17 by manipulating handles 15. The slitter frame 9 and the components mounted thereon, including top blade 10, make up what is known as the top slitter assembly. The web slitter 8 also includes a bottom band 12 that is rotated by a motor 13.
During operation, top blade 10 is positioned or "side loaded" so that it lightly engages the side edge of bottom band 12. The leading point of contact between top blade 10 and bottom band 12 forms a cutpoint whereby the paper web is cut. As a result, top blade 10 and bottom band 12 overlap to provide a scissors-like action for cutting the web as it unwinds from a roll and is pulled through the web slitter by a take-up roll. A plurality of web slitters may be connected to create parallel paper strips of various widths.
After a period of use, top blade 10 becomes dull and requires replacement. In order to "change-out" the top blade 10, the operator first raises the top blade 10 away from bottom band 12, as illustrated in FIG. 1. The top blade 10 is secured to the hub 14 of slitter 8 by a locking ring 16. In order to remove locking ring 16, the operator first loosens the clamping screw 20. Then, a locking ring removal/locking tool is used to free the hub 14. Locking ring 16 then may then be unscrewed by hand from hub 14. Once locking ring 16 is removed from hub 14, as illustrated in FIG. 2, the operator may remove top blade 10.
Once the new blade is positioned on hub 14, the reverse procedure is performed to complete the blade change-out process.
Currently, paper mill operations people frequently find it difficult to complete a blade change-out using the above procedure. More specifically, an operator is required to use two hands when using the locking ring removal/locking tool. One hand is used to hold the tool in engagement with the locking ring while the other hand is used to turn or apply leverage to the tool. However, the tool does not prevent the hub from rotating. The operator is thus required to hold the blade so that it doesn't turn while operating the tool. As a result, the operator must steady both the tool and blade with one hand while simultaneously turning the tool with the other hand. This task can be both difficult and time consuming.
In the operation of high speed machinery, such as in paper manufacturing, the cost of machine downtime can be very high. As a result, it is desirable to minimize the time that it takes to perform maintenance operations. One way to minimize machine downtime is to reduce the time necessary to perform blade change-outs. If a web slitter was equipped with mechanisms to prevent the blade 10 from rotating during a blade change-out, operators could perform the task more quickly and safely. As a result, it is desirable to provide web slitters that may be locked to prevent rotating during blade change-outs and other maintenance procedures.
Previous blade locking mechanisms, such as those provided by the Economy Machine and Tool Company of Green Bay, Wis. have utilized a pin with a cable attached. The operation of such mechanisms involve inserting the pin through aligned holes in the hub and slitter frame. As a result, the hub and top blade are prevented from rotating. A disadvantage of this arrangement, however, is that should the pin be left engaged when the top blade is lowered and/or used for slitting, severe damage to the slitter and injury to the worker could result. In addition, lost production could occur due to an uncut or random cut paper roll.
Another type of locking mechanism involves the use of a spring plunger that engages a hole in the hub when the plunger is extended. Such mechanisms are available from the Tidland Corporation of Camas, Wash. and the Diennes Corporation of Spencer, Mass. The operator must hold the plunger in engagement with the hole in the hub, however. As a result, this mechanism does not free up both of the operator's hands.
Accordingly, it is an object of the present invention to provide a device and method for locking a slitter blade so that an operator may use both hands to perform blade change-outs and other maintenance.
It is another object of the present invention to provide a device and method for locking a slitter blade so that blade change-outs and maintenance may be performed more rapidly and safely.
It is another object of the present invention to provide a device and method for locking a slitter blade whereby the blade is automatically unlocked when the blade is engaged for slitting.
It is another object of the present invention to provide a device and method for locking a slitter blade that is simple to manufacture and easy to use.
It is still another object of the present invention to provide a device and method for locking a slitter blade that may be used with existing web slitters.